18wks pregnant, red blood light flow for past 4 days, now passing small clots ,no pain , babys heartbeat heard but told expect worse,will i miscarry?

Pregnancy viability: At 18 weeks, second trimester bleeding reflects the adequacy of the placenta to support the fetus. It can represent a placental bleed, or abrupt ion, which can lead to death of the fetus. Many women experience second trimester bleeding and go on to have a viable baby. You need to speak to your obstetrician, and go in to make sure the heartbeat is heard over the next week.